Risk of bias in individual studies
Study quality was assessed independently by two reviewers based on the
seven domains defined by the Cochrane Collaboration’s tool for assessing
risk of bias.14 The tool includes the following
domains: random sequence generation, allocation concealment, blinding of
participants and personnel, blinding of outcome assessment, incomplete
outcome data, selective reporting, and other sources of bias. We rated
each domain as low risk, unclear risk, or high risk of bias. We assigned
individual trials as high risk of bias if one or more domain(s) was
deemed high risk of bias; otherwise, we assigned individual trials as
low risk of bias.